The present invention is in a maintenance monitor and more specifically in programmable maintenance monitors. The monitor serves to automatically advise that maintenance of equipment should be undertaken.
U.S. Pat. No. 4,025,774 discloses an electronic system employing a calculator as an arithmetic unit and accumulator. Present values of time are entered on a keyboard in the chosen mode of timer or stop clock. Sequencing circuitry gates the output of an oscillator to provide time increment pulses. A visual display indicates accumulated time in both modes. When employed as a timer, an audible signal is produced when a preset time has elapsed. However, this patent offers little by way of practical application of the disclosure thereof.
U.S. Pat. No. 3,758,756 discloses a miniaturized recorder and display device which receives data from operating engine sensors and activates the appropriate indicator to display the same. The device disclosed by this patent is adapted to provide a history of operation and to display present operating conditions and does not provide means for automatic indication of maintenance requirements.
U.S. Pat. No. 4,031,363 discloses a display apparatus for automotive vehicles which, among other things, can advise the operator of when, in miles or in days, service is again to be performed. However, the device is not suitable for indicating actual operating time of the vehicle.
U.S. Pat. No. 4,135,246 discloses an integrated history recorder for a gas turbine engine with numerous output displays indicating engine running time. The underlying motivation for such a measurement is based on the fact that the reliable operational life of such an engine is inversely related to the temperature and duration of temperature at which the gas turbine engine operates. The reference discloses use of a mechanical digital counter to provide an accumulative indication of engine run time.
U.S. Pat. No. 4,159,531 discloses a solid state unit useful in maintenance of a motor vehicle which provides a reminder of the next maintenance mileage point as well as which items are to be serviced. However, the device is equipped with a programmable read only memory capable of storing eight bit data words but has no capacity for accumulation of operational information.